Copper oxide rectifier



Aug. 29, 1933, A. L. ATHER'roN COPPER OXIDE RECTIFIER Filed Dec. s1,1927 INVENToR Y y k AT'ToRNEY Patented Aug. 29, 1933 UNITED STATESPATEN'I'I OFFICE.

1,924,300 corran oxma asoma Alfred L.

Atherton, Verona, Pa., assigner to Westinghouse Electric & ManufacturingOompany, a Corporation of Pennsylvania Application December 3l,l 1921Serial No. 243,904 l 15 Claims. (CL175-368) 4 surfaces placed in contactwith terminal plates of i a different metal. n

yOne object of my invention is to produce rectifiers or other deviceslikely to be heated, and which Vcomprise a metal and a compound thereofwith a conducting contact material therefor, 1 which shall lundergo nogradual change during their life.

A further object of my invention is to produce oxidized copperrectiflers which shall not -deteriorate or otherwise change theirelectrical 5 characteristics during use. Other objects of my inventionwill be apparent upon reading `the following specification, taken inconnectionwith the appended drawing in which is shown an oxidized copperrectiiier provided with contacts in accordance with my invention.

In the present art, rectiiiers comprising discsl of copper or othermetal having formed on one surface a layer of some chemical compound,such as an oxide, are well known.- It appears that the junction betweenthe oxidized layer and the mother metal possesses the property ofunilateral conductivity. In consequence of this, if an alternatingelectromotive force of proper magnitude o is impressed in series withthis junction, a uni directional current is caused to flow in the cir--Acuit. A problem, however, is presented of making contact between theexternal surface of the oxidized layer and the remaining conductors ofthe electric circuit.

One solution of this problem has been found through the use of washersof lead or other impressible metal which readily conform to the L0oxidized surface and make lfair electrical contact therewith. However,it has been found that, when contacts are made in this manner, theelectrical resistivity of the combined unit gradually i rises inthecourse of its operative life'. For many l purposes, the resistancerise just mentioned is undesirable and the present invention provides amethod of making contact which avoids it'.

While my invention is not, in any way, defpendent upon the correctnessof the following` theory, it appears probable thatthe rise in resistanceis the result of the oxidation of the impressible lead washer under theinfluence of heat generated within the body of the rectifier unit whenin use. It further appears probable that a part, at least, of theoxidation necessary to the foregoing reaction comes from the/layer ofoxidized metal. In accordance with my invention, I prevent the gradualoxidation of the. metallic washer by forming its surface of a material.which is chemically inert to oxidation at the operatingv temperaturesof the rectifier. .i0 As specific methods of giving effect to this ifundamental idea, I may form the washer of some soft metal, such asnickel, which is chemically inert to oxidation at ordinary temperatures.Alternatively, I may employ a washer of somesoft .55 metal not thuschemically inert but having its surface coated by electroplating orotherwise with a thin film of metal inert to oxidation. In a stillfurther modification, I may coat the surface of the metal with acompound of the very element 79 which combines with the rectifier metalto form the active surface compound thereof. For example, in the case ofan oxidized copper rectifier, I may use a lead washer, the surface ofwhich has been subjected to a preliminary oxidation. E In the drawing,Figure iis a sectional view of a rectifier embodying my invention andFigs. 2 and 3 are sectional views of modified single recti- A'ilerelements. In Figure 1 is shown a rectiner so. l

comprising three component elements, each of which consists of ametallic base 1, which may be of copper, and which has a layer 2 of somecompound formed on one surface. When copper is used, this compound maybe the oxide. United BtatesfPatent 1,640,335 discloses waysl of making`auch" oxidized copper rectifier units. `In contact with vthe oxidelayer2 is a washer 3 consisting of lead, the contacting surface of which haspreviously been provided with an oxidized layer 4.

Any desired number of component units such as that just described may becombined to form a circuit element possessing unilateral conductivity.

- If an alternating electromotive force is impressed between theterminal discs 5 and 6. current will/'be 95 transmitted freely in thatdirection in which the :L y copper is negative in potential to itsoxidized layer and scarcely at all in the reverse direction. Any desirednumber of the above described discs may be mounted on a through bolt '1having an insu- 100 lated covering '8, as indicated. 4 9;.

In another `modification shown in Fig. 2, the contacting washersconsists entirely of an impressible metal which is chemically inert tooxidation below 200 C., for example, gold or nickel.

In a third modification shown in Fig. 3, the contact washers 10 mayconsist of lead or other soft metal having a coating such as nickeloi'tgold which is chemically inert to oxidation at temperatures below200 C..

Accordingly, by means of my invention, I proments of my invention, thebroad principles of such character as to' undergo no change inelectrical characteristics during the operative life of the rectifier.

Where in the following claims the expression common metal occurs, it isused .to designate metals which are readily obtainable and, therefore,inexpensive as distinguished from the rare metals such as gold, platinumand the like.

While I have here described particular embodithereof are otherwiseapplicable in ways which will be apparent to those skilled in the art. Idesire, therefore, that the terms of the following claims shall be giventhe broadest interpretation of which they are .susceptible in View ofthe limitations of the prior art. i

I claim as my invention:

1. In a rectifier of the type comprising a metal and an oxide of saidmetal thereon, a contact element cooperating with said compound andhaving a surface of a composition of common metal, said compositionbeing devoid of chemical'afl'inty Vfor said oxide.

Y 2. In a rectifier of the type comprising a metal and a compoundthereof With another substance formed thereon, a contact elementcooperating with said compound and comprising a common metal chemicallyinert to said compound at all temperatures at which the rectifieroperates.

3. In a rectifier of the type comprising a metal and a compound thereofwith another substance formed thereon. a contact element cooperatingwith said compound and comprising an impressible common metal chemicallyinert to said compound at all temperatures at which the rectifieroperates.

4. In a rectifier of the type comprising a surface of metal havingoxygen in combination therewith, a contact element cooperating with saidsurface and comprising a composition of common metal,

and a compound thereof with a non-metallic element, a contact elementcooperating with said ff; compound and comprising an impressiblecomvidean oxidizedmetal rectifier with contact plates '7. VIn arectifier of the type comprising ametal and an oxide thereof, a contactelement cooperating with said oxide and comprising a surface layer of acomposition of common metal, said composition having no tendency toreduce said oxide.

. 8. In a rectifier ofthe type comprising a metal and an oxide thereof,a contact element cooperating with said oxide and comprising a commonmetal chemically inert to said oxide at all temperatures at which therectifier operates.

9. In a rectifier of the type comprising a metal and an oxide thereof, acontact element cooperating with said oxide and comprising animpressible common metal chemically inert to oxidation at alltemperatures at which the rectifier operates.

10. In a rectifier of the type comprising copper and an oxidized layerthereof formed thereon, a contact element cooperating with said layerand' comprising a composition of common metal, said composition beingdevoid of tendency to take up oxygen from said layer. I

11. In a rectifier of the type comprising copper and an oxidized layerformed thereon, a contact element cooperating with said layer andcompris-- ing a common metal chemically inert to said layer at alltemperatures at which the rectifier operates.

12. In a rectier of the type comprising copper and an oxidized layerformed thereon, a contact element cooperating with said layer andcomprising an impressible common metal chemically inert to said layer atall temperatures at which the rectifier operates.

13. In combination with a metal and an oxide of said metal thereon andsubject to heat, a contact element cooperating with said oxide andhaving a surface layer of a composition of common metal, saidcomposition having less chemical aflinity for said oxide than said metalhas.

14. In combination with a metal and a compound thereof withanother-substance' formed thereon and subject to heat, a contact elementcooperating with said compound and comprisingA a common metal chemicallyinert to said compound at all temperatures to which said substances aresubjected.

15. In combination with a metal and a-compound thereof .with anotllersubstance formed thereon and subject to heat, a contact elementcooperating with said compound and comprising an impressible commonmetal chemically inert to said compound at all temperatures to whichsaid substances. are subjected.

\ ALFRED L. ATHER'IION.

